Safety needle and syringe assembly

ABSTRACT

A disposable safety needle and syringe assembly includes a needle shield movably positioned within a syringe housing. Movement of the needle shield from the housing is effected by movement of the syringe plunger and plunger piston following completion of an injection whereby the needle shield envelopes the needle extending from the housing to prevent accidental needle sticks. The plunger piston is disengagable from the plunger at a limit of travel upon retraction of the plunger, thus maintaining the shield in a locked position enveloping the needle. The syringe and needle assembly can then be safely handled for disposal, and the possibility of inadvertent reuse of the needle and syringe is eliminated.

BACKGROUND OF THE INVENTION

This invention relates generally to hypodermic needles and syringes, and more particularly the invention relates to a disposable syringe and safety needle assembly.

The safe use and disposal of hypodermic needles and syringes are concerns in the medical and health professions. Needle stick injuries following use of a needle pose a risk to both patient and user, and especially with the present risk of HIV and hepatitis infection, care must be taken in the safe handling and disposal of used needles and syringes. A safety cover for the used needle is a recognized requirement.

A number of safety syringe designs incorporating needle covers have been proposed. U.S. Pat. Nos. 4,909,791 and 4,982,842 employ jaw members pivotally mounted on a syringe barrel for covering a needle after use.

U.S. Pat. Nos. 4,883,471 and 4,935,014 disclose syringe assemblies in which the needle is drawn into the syringe after use.

U.S. Pat. No. 4,969,877 discloses a syringe assembly in which an outer casing is provided around an inner chamber or syringe portion which slides in the outer casing to an operational position and to a retracted position at the forward and rearward ends of the outer casing, respectively.

U.S. Pat. No. 4,874,382 uses the body of a syringe as a protective shield into which a needle is drawn after use. A spring biasing mechanism is required in drawing the needle into the sheath.

U.S. Pat. No. 4,863,435 incorporates an outer shield which is spring biased to slide on the syringe to cover a needle after use and which is retractable on the syringe to permit needle injections.

While each of these safety syringes provides some protection against accidental needle injury, the designs require a relatively complex mechanism, are bulky in handling and use, and expensive to manufacture. Moreover, actuation of the safety features can require use of both hands of the health care worker.

The present invention is directed to an improved safety needle and syringe assembly which overcomes limitations of the prior art.

SUMMARY OF THE INVENTION

Accordingly, an object of the invention is an improved safety needle and syringe assembly.

Another object of the invention is a safety needle and syringe assembly which is simple in design and readily manufacturable.

Still another object of the invention is a safety needle and syringe assembly in which the user's hand remains behind the needle at all times during and after use without changing finger position used during an injection.

A feature of the invention is an integral shield positioned within a syringe housing and which is moved to cover the needle following an injection by the plunger within the syringe housing.

Briefly, a disposable syringe and needle assembly in accordance with the invention is conventional in appearance and handling. A small rigid retractable needle shield is provided in the syringe, and following an injection the needle shield can be easily and quickly extended to a locked position covering the needle. Extension of the shield to the locked position is accomplished by pressing the syringe plunger past the zero volume point into engagement with the needle shield which is then pushed from one end of the syringe housing until it locks at the end of the syringe barrel. The syringe and needle assembly can then be safely handled for disposal. Further, the possibility of inadvertent reuse of the needle is eliminated due to the covered needle.

In a preferred embodiment, the needle includes an inner portion within the syringe housing which extends through a forward seal around one end of the shield. The plunger includes a central bore having an axial length to accommodate the inner portion of the needle. Following an injection, the piston of the plunger engages the end of the inner portion of the needle and the forward seal. As the piston pushes the forward seal and shield toward the end of the housing, the inner portion of the needle is received in the axial bore of the plunger. Thus, actuation of the shield is effected by the same one hand operation as the injection by further movement of the plunger and piston.

In a preferred embodiment, the needle support has spaced lugs or ribs which engage the inner wall of the syringe housing. The needle shield is segmented with shield segments passing between the support ribs during extension of the shield.

The invention and objects and features thereof will be more readily apparent from the following detailed description and appended claims when taken with the drawings.

BRIEF DESCRIPTION OF THE DRAWING

FIGS. 1A-1C are side views of a needle and syringe assembly in accordance with one embodiment of the invention before use, after use, and after shield extension, respectively.

FIG. 2 is a side view of the plunger stem as used in the assembly of FIG. 1.

FIGS. 3A and 3B are end and side views of the plunger piston in the syringe of FIG. 1.

FIGS. 4A and 4B are an end view and side view of the needle shield in the syringe of FIG. 1.

FIG. 5 is a section view of the needle shield taken along the line 5--5 in FIG. 4A.

FIGS. 6A and 6B are an end view and a side view in section of the needle support and syringe barrel, respectively.

FIGS. 7A and 7B are an end view and a section view of the shield piston.

FIGS. 8A-8D are side views in section illustrating assembly of the syringe and needle assembly of FIG. 1.

FIGS. 9A-9D are side views in section illustrating operation of the syringe and safety needle assembly of FIG. 1.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Referring now to the drawing, FIGS. 1A-1C are side views of a needle and syringe assembly in accordance with one embodiment of the invention prior to injection, after injection, and after extension of a needle shield. The assembly includes a syringe 10, a plunger 12, a needle 14 extending from one end of the syringe 10 and a shield 16 positionable about the needle 14 and extending from the one end of the syringe 10 from which the needle 14 extends.

The user inserts the needle into a patient and injects the contents thereof by pushing plunger 12 as shown in FIG. lB. The needle can then be removed from the patient while the plunger 12 is pushed further into the syringe 10 thereby pushing the needle shield 16 from the syringe and covering the needle. The syringe and needle assembly can then be safely handled for disposal. Further, with a covered needle the possibility of inadvertent reuse of the needle and syringe is also eliminated.

An important feature of the needle and syringe assembly in accordance with the invention is that the use and appearance thereof are almost unaffected by inclusion of the needle shield. Further, needle protection can be accomplished without changing finger positions used during injection with an easy one-handed operation. Importantly, as will be described further hereinbelow, the needle and syringe assembly requires few parts which translates to low production cost.

FIG. 2 is a view of the plunger stem used in the syringe of FIG. 1. The plunger 12 includes an extension 20 with a central bore 22 extending through the extension into the plunger 12. The central bore receives an inner portion of the needle as will be described hereinbelow. The extension 20 includes a disk shaped head which is received in an opening in the pliable plunger piston shown in FIGS. 3A, 3B. The plunger piston 24 is a disk shaped body as illustrated in the end view of FIG. 3A which has a cavity 26 in one side thereof for receiving the disk shaped head of extension 20 of plunger stem 12. The piston can be made of a pliable rubber, for example.

FIGS. 4A and 4B are an end view and a side view, respectively, of the needle shield which may comprise a hard plastic material. The shield includes a plurality of segmented portions 30 which support a generally hemispherical end portion 32 having a hole 34 therein for receiving the needle. FIG. 5 is a section view of the needle shield taken along the line 5--5 of FIG. 4A. The shield has outer detents 36 and inner detents 38 on one end which serve to limit the extension of the shield from the syringe body following an injection.

FIG. 6A and FIG. 6B are an end view and side view in section of the needle, needle holder, and syringe body. The needle 14 is mounted in a support 42 having a plurality of ribs or lugs 44 which engage the inner surface of the syringe housing 10. Alternatively, the lugs 44 can be integral with the syringe housing and receive the support 42. The needle 14 has an inner portion extending within the housing 10 and an outer portion for insertion in a patient. FIGS. 7A and 7B are an end view and side view, respectively, of a shield piston used in pushing a shield from a syringe following an injection. The piston can be made of hard rubber.

Consider now FIGS. 8A-8D which are side views in section illustrating the assembly of the needle and syringe. In FIG. 8A the needle 14 and support 42 are inserted in one end of the syringe housing 10, and the shield 30 is then inserted in the housing 10 with the segments of the shield passing between the ribs of the needle support. The segments must be flexed so that the detents of the shield can pass inner detents 44 projecting from the inner surface of housing 10.

In FIG. 8B, while the shield 30 is held in place, the shield piston 46 is inserted from the opposing end of the syringe housing until the piston engages the end of the shield segments 30 and the inner end of needle 14 passes through the central portion of the piston. In FIG. 8C the plunger and piston are assembled, and the plunger assembly is then inserted into the syringe body as shown in FIG. 8D. The completed syringe is now ready for use.

FIGS. 9A-9D are side views in section illustrating operation of the needle and syringe assembly. FIG. 9A shows the assembled syringe prior to use and as shipped from a factory. The plunger 12 is inserted in the housing to a point where the plunger piston 24 contacts the shield piston 46.

When used, liquid is drawn into the syringe as illustrated in FIG. 9B by withdrawing the plunger 12. After injection has been completed, further pressure on the plunger piston 24 moves the shield piston 46 and extends the shield 30 from one end of the syringe 10 over the needle 14 as shown in FIG. 9C. The rubber plunger piston 24 and the shield piston 46 become locked between the detents 44 on the inner surface of the syringe housing 10, and the inner portion of the needle 14 pierces the plunger and is accommodated in the central bore 22 in the plunger stem 12.

Retraction of the plunger 12 results in separation of the plunger stem and plunger piston while the shield 16 remains intact over the external portion of needle 14. The shield 16 remains in a locked position due to the plunger piston 24 and shield piston 46 being locked between the detents 44 on the inner surface of the syringe. Thus, the needle shield is easily and quickly extended to a locked position completely covering the needle by simply pressing the syringe plunger past the zero volume point until it locks at the end of the syringe barrel.

There has been described a new and improved disposable syringe and safety needle assembly which is economical to manufacture, easy to manipulate during use, and provides protection against unintended needle penetration or related trauma with inherent potential for the spread of infectious disease.

While the invention has been described with reference to a specific embodiment, the description is illustrative of the invention and is not to be construed as limiting the invention. Various modifications and applications may occur to those skilled in the art without departing from the true spirit and scope of the invention as defined by the appended claims. 

What is claimed is:
 1. A disposable safety needle and syringe assembly comprisinga syringe including a housing having opposing open ends, a plunger and plunger piston movably positioned within said housing from one end, a needle and needle support positioned at the other end of said housing with said needle including an external portion extending from said housing, and a needle shield movably positioned within said housing from said other end, said needle shield being movable from and extending out of said housing by movement of said plunger and said plunger piston following completion of an injection whereby said needle shield envelopes said needle portion extending from said housing to prevent accidental needle sticks.
 2. The disposable safety needle and syringe assembly as defined by claim 1 wherein said needle includes an internal needle portion within said housing, a shield piston around said internal needle portion and abutting said needle shield, said shield piston defining one wall of a fluid cavity within said syringe, said shield piston being engagable by said plunger piston in moving said needle shield from said housing.
 3. The disposable safety needle and syringe assembly as defined by claim 2 wherein said plunger includes a central bore for receiving said internal needle portion as said plunger and said plunger piston move said needle shield from said syringe housing.
 4. The disposable safety needle and syringe assembly as defined by claim 2 wherein said needle support includes a central portion with a plurality of ribs supporting said central portion in an inner surface of said syringe housing, said needle shield including a plurality of segments each positioned between two of said ribs.
 5. The disposable safety needle and syringe assembly as defined by claim 4 wherein said needle shield further includes a generally hemispherical end portion supported by said segments outside of said syringe housing, said end portion including a hole through which said needle extends.
 6. The disposable safety needle and syringe assembly is defined by claim 5 wherein said syringe housing includes detents on said inner surface, said shield piston and said plunger piston being limited in travel within said syringe housing by said detents.
 7. The disposable safety needle and syringe assembly as defined by claim 6 wherein said plunger piston is restricted from retraction from a limit of travel by said detents.
 8. The disposable safety needle and syringe assembly as defined by claim 7 wherein said plunger piston is disengagable from said plunger at said limit of travel upon withdrawal of said plunger from said syringe housing.
 9. The disposable safety needle and syringe assembly as defined by claim 2 wherein said syringe housing includes detents on said inner surface, said shield piston and said plunger piston being limited in travel within said syringe housing by said detents.
 10. The disposable safety needle and syringe assembly as defined by claim 9 wherein said plunger piston is restricted from retraction from a limit of travel by said detents.
 11. The disposable safety needle and syringe assembly as defined by claim 10 wherein said plunger piston is disengagable from said plunger at said limit of travel upon withdrawal of said plunger from said syringe housing. 